Sejournet



March 24, 1964 J. SEJOURNET 3,126,097

METHOD AND APPARATUS FOR HOT EXTRUDING METALS AND ALLOYS Filed July 27, 1962 2 Sheets-Sheet 1 March 24, 1964 SEJOURNET 3,126,097

METHOD AND APPARATUS FOR HOT EXTRUDING METALS AND ALLOYS Filed July 27, 1962 2 Shets-Sheet 2 Fig.4

United States Patent 3,126,097 METHOD AND APPARATUS FOR HOT EXTRUD- MG METALS AND ALLOYS Jacques Sejournet, Paris, France, assignor to Societe Anonynre Compagnie du Filage des Metaux et des Joints Curty CEFILAC, Paris, France, a corporation of France Filed July 27, 1962, Ser. No. 212,935 (Ilaims priority, application France Mar. 20, 1962 Claims. (Cl. 207-) This invention relates to a method for hot extruding metals and alloys at elevated temperatures.

For many years hot extrusion has been used to shape and form metals and alloys, there being placed between the billet and the die a vitreous lubricating substance that partly or completely melts at the operating temperature, while, nevertheless, remaining viscous. It has been suggested, in addition, to surround the billet with a thin layer of the same vitreous substance before introducing it into the container. Finally, in the extrusion of tubes, it has been found advantageous to place a layer of glass between the mandrel and the interior surface of the billet. Nevertheless, until now it has been practically obligatory to use a flat or only slightly concave die with interposing a cold mass of vitreous lubricant between the cold die and the hot billet. Under these conditions, the mass of lubricant protects the die and, under the effect of heat, covers the extnuded bar with a coating of melted vitreous lubricant as the bar passes into the die. A small amount of glass only is necessary for a successful operation and the major part of the original lubricant remains on the die. The industrial advantages thus obtained are numerous; but, in practice, certain precautions are necessary. For example, the extrusion speed must be carefully controlled. If it is too fast, not enough of the lubricant melts to completely protect the die, which thereby suffers from abnormally rapid erosion. If the speed is too slow, too much lubricant melts, which instead of covering the metal with a continuous thin layer, impresses itself into the metal and is extruded therewith, rendering the extruded bar useless, because of pits, cavities, holes, or other defects formed in its surface.

With a view to avoiding these difficulties, the applicant conceived the idea, that forms the basis of the invention, of enclosing before the beginning of extrusion an intermediate protective substance in a space provided between the billet and the tools, such space being of such shape that the substance ejected by the effect of the pressure exerted during the extrusion operation is forced under the form of a thin layer between the extruded product and the die. Under these conditions, it has been established that the successful operation no longer depends on the extrusion speed, but solely on the substance chosen and on the form of the space provided for it.

' The method of the invention for extruding metals and alloys, particularly at elevated temperatures, fundamentally consists in placing between tools and billet, before the beginning of the actual extrusion operation an inter mediate protective substance which, at working temperatures, provides a liquid or viscous non gasifiable layer between the container, the lateral surface of the billet, the entrance of the die and, at least, a part of the front face of the billet, whereby the said part of the front billet face and the die entrance are in contact along toric or truncated conical surface, the axial sections of which have a continuous curvature. The extrusion then begins in the customary manner.

The new arrangement for effecting this method is also an object of the invention, and consists of the combination of container, die, and billet, in which a clearance is provided between the billet and the container, and in which the billet is chamfered at its front part, in the shape of ICC a conical frustum or of a tore, for example, and the face of the die takes the form of a depression or cavity that is in tangential touching relationship with the chamfer of the billet.

If the billet is to be extruded in a tube or a hollow bar, the billet is prepierced, its bore and/or the corresponding mandrel is lubricated in the usual manner.

In one preferred embodiment of the invention, the clearance (diiference in diameters) between billet and container is comprised between 3 and 8% of the billet diameter. The shape of the front part of the billet is substantially that of a truncated cone or tore. The entrance of the die also has a truncated conical or toric shape in connection with that of the billet, thereby to assure the desired contact between the two. This results in a substantially tangential relationship between the surfaces of the die and billet, at the point of contact.

From the optimum amount, experimentally determined, of the intermediate protective substance required to assure a correct operation of the extrusion, the volume of the space holding the substance is fixed. In order to assure a substantially constant flow of the substance during extrusion, the longitudinal contours of the billet and die are also determined. Among other factors these contours are a function of the characteristics of the metal or alloy and of the substance, and a function of the dimensions of the billet and extruded bar.

Substances that can be used as intermediate protectors consist, within the scope of the invention, of all salts that do not react with the metals in presence, and which liquify but do not vaporize or gasify at the working temperature, as well as of glasses and enamels that become viscous at this temperature. By way of example only, the following substances are listed: barium chloride, sodium sulphate, sodium bo rate, sodium phosphate, sodium silicate, lithium carbonate, ordinary window glass, special glasses, or combinations of some or all of these substances.

In the method, the desired amount of the chosen substance is applied to the outer surface of the billet. When the billet is placed into the container, the substance is held behind the line of contact between billet and die.

It is also Within the scope of the invention that there can be placed, in a known manner, between the dummy block and the rear of the billet, a plate or pad of the same substance, the melting of which, during the extrusion, adds in the desired degree to the substance confined in the clearance space between the billet and container.

The invention will now be described in detail; with particular reference to the accompanying drawings taken along a plane including the axis of the billet and of the die, in which:

FIG. 1 shows a known arrangement, in operation, for hot extruding metals and alloys;

FIG. 2 shows an arrangement, before hot extnusion, designed according to the invention;

FIGS. 3 and 4 are detailed views of the operation in accordance with the invention at the beginning, and during the course, of the extrusion, respectively;

FIGS. 5 to 7 illustrate diiferent advantages relationships between die and billet, according to the invention.

For the purpose of comparison with the method of the invention, the known scheme of operation will be briefly recalled. FIGURE 1 shows a known arrangement for extruding with glass lubrication. Numeral 1 designates the container of an extrusion press in which a hot billet 2 has been introduced. The clearance (difference in diameters) between billet and container amounts to 4% of their diameters. Force is applied to the billet by a ram 4 (integral with the main piston of the press) through dummy block 3. The arrow indicates the direction of movement of the ram. Die 5 is in a die holder 6 and supported by a die support 7, which rests upon a metal block, not shown, rigidly secured with the bed of the press. Between the die and billet is a mass of vitreous lubricant 8, which, at first solid, superficially melts on contact with the hot billet, is deformed, and covers the surface of the extruded bar 9 with a thin layer of lubricant. In addition, a thin layer of lubricant 11, placed between billet 2 and container 1, reduces the friction between the two as the billet moves forward in the container.

The arrangement according to the invention is shown in FIGURE 2. In this arrangement, the clearance 12 (difference in diameters) between billet 2 and container 1 amounts to 3 to 8% of their diameters. The front part of the billet 2 is chamfered in the shape of a toric surface 13. The entrance face of die 5 takes the form of a depression or cavity 14, the lips .15 of which are tangent at 16 to the toric surface. Before the introduction of the billet into the container, the intermediate protective substance 17 is applied to its periphery. When the billet has been introduced, the substance 17 occupies the space 3.2 as far as the line of contact 16, but not beyond it. The extrusion is accomplished in the customary manner, by means of ram or punch 4 and dummy block 3, and occurs in the direction of the arrow. The operating temperature causes the intermediate protective substance 17 to melt and, as a consequence of the forward force exerted on the bottom of the billet through dummy block 3, the billet is pressed forwardly. The substance 17 is forced across line 16 by the billet, which is covered with a thin protective film as it flows along cavity =14, then along die 5.

FIGS. 3 and 4 show an axial view, on an explained scale, of the lower part of one embodiment of the arrangement. Curve AB is a section of the surface joining the cylindrical portion 21 of the billet with its front face 22. Curve CDEF is a section of the surface of die 5. These two curves are tangent to each other at P, on line of contact 16. The area APC plus clearance space 12 define the volume where the intermediate protective substance is confined before the extrusion.

When billet 2 in container 1 has been pressed against die 5 under the action of the pressure exerted by the dummy block 3, the substance !17, confined in area APC, spreads between the billet, the container, and the die. The point of contact P is moved forward to the orifice DEF of the die. During the extrusion, a film 18 of the substance, squeezed by the pressure and carried along by the extruded bar 19, moves along the shaping portion EF of die 5 and covers the extruded bar with a uniform film 20.

The method of extruding according to the invention can employ various combinations of chamfer of the billet and of shape of the die. FIGURES 5 to 7 show three possible embodiments of the apparatus.

In FIGURE 5, lips and depression or cavity 14 of die 5 have a flared axial portion OD tangent at P, to the circular shoulder AB or billet 2.

In FIGURE 6, the depression 14 takes the form of a truncated cone and is connected to the shaping portion EF by shoulder DE. The chamfer of billet 2 remains an arc of circle AB.

In FIGURE 7, the depression 14- is flared, and the chamfer AB of billet 2 takes the form of a truncated cone. As can be seen, the depression 14 is substantially tangent to the chamfer.

By way of example and not in limitation thereof, the method has been used with a container of 122 mm. diam eter, a billet 300 mm. long and 115 mm. diameter, and

a die in accordance with the embodiment of FIGURE 7, having a bore diameter (part EF) of 20 mm. and a flare, the axial section of which was a quarter of a circle with a 40 mm. radius. One of the intermediate protective substances used was barium chloride in the amount of 300 grams, applied to the periphery of the billet before introduction into the container. The force upon the dummy block was 1000 tons, and there was extruded, without difficulty, a bar covered with a film of 0.1 mm. thickness.

What I claim is:

1. In a method of hot extruding metals and alloys, the invention comprising forming a billet to be extruded so that at least a portion of its leading end face has a substantially toric shaped surface extending substantially completely around said port-ion, heating said billet to hot extrusion temperature and introducing it into a container provided with a die at one end thereof, said die having an entrance face extending axially towards the orifice thereof, said introducing being such that said toric shaped surface engages said entrance face in a substantially tangential line of contact extending substantially completely around said toric face surface of said billet, said line of contact being between the periphery portion of said billet and the orifice of said die, said introducing being such that a space is formed between the lateral peripheral surface of said billet and the interior walls of said container and rearwardly of said line of contact, said space having a volume defined by a difference in diameters between said billet and said interior wall of said container of substantially about 3%8%, providing in said space an intermediate protective material substantially all of which is one of liquid and of non-gasifiable viscous liquid at said hot extrusion temperature, thereafter extruding said billet through said die so that during said extruding said material passes between said billet and said die and covers the product extruded with a continuous protective coating.

2. The method of claim 1 characterized by said material being selected from the group consisting of salts, glasses and enamels which do not react with said metals and alloys and which are liquid without vaporization or gasification at said hot extrusion temperature.

3. The method of claim 2 characterized by said salts, glasses and enamels being selected from the group consisting of barium chloride, sodium sulphate, sodium borate, sodium phosphate, sodium silicate, lithium carbonate, window glass and plate glass and combinations thereof.

4. The method of claim 1 characterized by in said extruding said line of contact moving toward said orifice of said die.

5. The method of claim 1 characterized by carrying out said extruding with a dummy block placed between the rear end of said billet and a ram.

References Cited in the file of this patent UNITED STATES PATENTS 2,343,036 Wilson Feb. 29, 1944 2,628,417 Peyches Feb. 17, 1953 2,630,220 Sejournet Mar. 3, 1953 2,761,204 Bannister Sept. 4, 1956 2,893,554 Sejournet et al. July 7, 1959 2,893,555 Buffet et al. July 7, 1959 2,907,454 Sejournet Oct. 6, 1959 2,932,390 Edgecombe Apr. 12, 1960 2,946,437 Edgecombe July 26, 1960 2,990,610 Luckenath et al. July 4, 1961 3,072,251 Sauve Jan. 8, 1963 

1. IN A METHOD OF HOT EXTRUDING METALS AND ALLOY,S THE INVENTION COMPRISING FORMING A BILLET TO BE EXTRUDED SO THAT AT LEAST A PORTION OF ITS LEADING END FACE HAS A SUBSTANTIALLY TORIC SHAPED SURFACE EXTENDING SUBSTANTIALLY COMPLETELY AROUND SAID PORTION, HEATING SAID BILLET TO HOT EXTRUSION TEMPERATUE AND INTRODUCING IT INTO A CONTAINER PROVIDED WITH A DIE AT ONE END THEREOF, SAID DIE HAVING AN ENTRANCE FACE EXTENDING AXIALLY TOWARDS THE ORIFICE THEREOF, SAID INTRODUCING BEING SUCH THAT SAID TORIC SHAPED SURFACE ENGAGES SAID ENTRACE FACE IN A SUBSTANTIALLY TANGENTIAL LINE OF CONTACT EXTENDING SUBSTANTIALLY COMPLETELY AROUND SAID TORIC FACE SURFACE OF SAID BILLET, SAID LINE OF CONTACT BEING BETWEN THE PRIPHERY PORTION OF SAID BILLET AND THE ORIFICE OF SAID DIE, SAID INTRODUCING BEING SUCH THAT A SPACE IS FORMED BETWEEN THE LATERAL PERIPHERAL SURFACE OF SAID BILLET, AND THE INTERIOR WALLS OF SAID CONTAINER AND REARWARDLY OF SAID LINE OF CONTACT, SAID SPACE HAVING A VOLUME DEFINED BY A DIFFERENCE IN DAIMETERS BETWEN SAID BILLET AND SAID INTERIOR WALL OF SAID CONTAINER OF SUBSTANITALLY ABOUT 3%-8%, PROVIDING IN SAID SPACE AN INTERMEDIATE PROTECTIVE MATERIAL SUBSTANTIALLY ALL OF WHICH IS ONE OF LIQUID AND OF NON-GASIFIABLE VISCOUS LIQUID AT SAID HOT EXTRUSION TEMPERATURE, THEREAFTER EXTRUDING SAID BILLET THROUGH SAID DIE SO THAT DURING SAID EXTRUDING SAID MATERIAL PASSES BETWEEN SAID BILLET AND SAID DIE AND COVERS THE PRODUCT EXTRUDED WITH A CONTINUOUS PROTECTIVE COATING. 